by Bart Jansen, USA TODAY

by Bart Jansen, USA TODAY

Although 10 countries are frantically searching for missing Malaysia Airlines Flight 370, Malaysia will likely lead the investigation unless it defers to another country, such as the United States, according to crash investigators and lawyers.

The International Civil Aviation Organization, a part of the United Nations based in Montreal, has an agreement that dictates who leads and participates in the investigation such as this: which involves a state-owned airline; another country, China, with most of the passengers on board; and the United States, a third country that is home to the Boeing 777 manufacturer.

Under ICAO, the location of the mishap dictates who leads the investigation. This is why the U.S. National Transportation Safety Board is leading for the Asiana Airlines crash in San Francisco in July.

But if the crash occurred in international waters such as the Gulf of Thailand, where the search is focused, international law dictates that the plane's country of registry - Malaysia - will lead the investigation.

"It's actually pretty specific in terms of how the investigation gets structured," said Mark Dombroff, who practices aviation law in the Washington office of McKenna Long & Aldridge.

Other countries with an interest in the incident can participate. The NTSB, which has already sent a team to Malaysia, would be invited to participate as an accredited representative because the U.S. is home to the manufacturer, while Boeing and the Federal Aviation Administration would also contribute their expertise.

The open question is whether Malaysia would ask another country such as the U.S. to lead the investigation. One reason would be cost. This investigation could cost $50 million or more, after it cost 20 million euros just to find the black boxes in the Air France flight 447 crash in the Atlantic in June 2009, according to crash experts.

The investigation of the TWA 800 crash off Long Island in July 1996 forced Congress to appropriate an extra $29 million to NTSB in 1997, amid several years of higher budgets for the agency.

William Waldock, a professor in safety science at Embry-Riddle Aeronautical University in Arizona, said Malaysia doesn't have a large investigative authority, so he expects them to ask NTSB to lead the case.

"That's exactly what I think they're going to do," Waldock said.

After the October 1999 crash of EgyptAir flight 990 off Massachusetts, which killed 217 people aboard, Egypt asked the NTSB to investigate for lack of resources.

But the request can backfire. Egypt wasn't satisfied with the NTSB's conclusions that the relief first officer nosed the plane downward into the ocean, and fought them for years in court.

"There is a mechanism to start, but no real mechanism to turn it off," Waldock said.

Even the most sophisticated investigators can disagree about their conclusions, such as when Turkish Airlines flight 1951 crashed near Amsterdam in February 2009, killing nine and injuring 117.

The Dutch Safety Board blamed the crash on a faulty altimeter that automatically slowed down the plane before it stalled and hit the ground. But NTSB investigators said pilots could have recovered if the crew detected and responded to the low decreasing airspeed.

The Malaysia investigation can begin informally even before wreckage is found.

Documentation of luggage and cargo loaded on the plane can be reviewed for possible hazards. Passenger and crew records, and maintenance and flight records, will also be scrutinized.

"That is something that not only the airline wants to look at, but certainly something the investigation is going to look at," said Dombroff, the lawyer. "You immediately start to gather not only the maintenance records for the aircraft, but all the training records for the crew."

Despite the cost and complexity of the search and investigation, participants want to determine what went wrong to prevent it from happening again.

"If if turns out there was something wrong with the airplane, some sort of major malfunction with the flight-control system, you need to know it because it might be an issue with other airplanes," Waldock said. "To lose that many people in one fell swoop, they want to account for everything. They want to put it to rest."